1. Field of the Invention
This invention relates to a superheated steam apparatus for processes such as sterilization, food preparation or the like, which use superheated steam that is generated from water vapor at atmospheric pressure.
2. Description of the Related Art
Superheated steam is used for sterilization for example. When superheated steam is used at normal pressure or atmospheric pressure, it is not necessary to have a structure for high pressure such as a high-pressure boiler or high-pressure container, so construction of the facility or equipment is simplified and safety increases and the need for regulatory inspection or control becomes unnecessary or becomes simplified.
A sterilization apparatus using this kind of superheated steam at atmospheric pressure has been disclosed in U.S. Pat. No. 4,263,258. This sterilization apparatus comprises a heat-insulated container that is filled with a heat-transfer medium and also is equipped with a sterilization chamber, and a water conduit through which the heat-transfer medium passes, and is capable of heating the heat-transfer medium to 100xc2x0 C. or greater. The water conduit comprises an evaporation section for converting the water into steam, and a steam-heating section for converting the steam into superheated steam, and it is connected to the sterilization chamber. The water that is supplied by way of the water conduit is vaporized in the conduit to become steam, and then is further heated to become superheated steam. This superheated steam is supplied to the inside of the sterilization chamber from one end of the water conduit where it sterilizes the object inside the chamber.
However, in the sterilization apparatus described above, there is a water conduit located inside the heat-insulated container, and this water conduit is heated by the heat-transfer medium, whereby the water in the water conduit is vaporized to steam and then the steam is further heated inside the water conduit until it becomes superheated steam, after which this superheated steam is then further directed through the water conduit to the sterilization chamber, so there is large heat loss of the heat-transfer path to the inside of the water conduit and heating energy is not efficiently used for generating superheated steam and is wasted.
Taking the problems of the related art into consideration, the object of this invention is to provide a superheated steam apparatus that is capable of efficiently heating water to generate superheated steam, and to perform a process such as sterilization utilizing this superheated steam while keeping the loss of heating energy to a minimum.
In order to accomplish the object above, this invention provides a superheated steam apparatus comprising; a processing section at the top on the inside of a housing container, which is at atmospheric pressure, for performing a process utilizing superheated steam and which includes a steam discharge outlet, and a superheated steam generation section located at the bottom of the processing section; and where the superheated steam generation section generates superheated steam or moist air inside the housing container, that is essentially in an open state, and is connected with the processing section in an open state.
With this construction, superheated steam is generated inside the housing container in an open state. In other words, the superheated steam that is generated is not enclosed in a separate sealed space inside the conduit inside the container or in the container, but actually spreads and fills the entire inside of the container. This superheated steam generation section is not separated from the processing section at the top but is connected, and the superheated steam enters the processing section in an open state. That is, the superheated steam generation section and the processing section are not separated at all, or in the case that they are separated, there is plenty of open area for sufficient circulation such that neither the heat loss nor resistance to flow are affected. For example, the sections may be separated by the support plate of the object to be processed or by a partition, and the superheated steam that is generated enters the processing section where processing such as sterilization or cooking is performed, without heat loss or flow resistance.
In this case, depending on the purpose of the apparatus or the operating conditions, it is possible for the superheated steam generation section to generate moist air that is 100xc2x0 C. instead of steam in the superheated region that is 100xc2x0 C. or greater. Depending on the purpose, it is possible to obtain sufficient sterilization results by using this kind of moist air as well. In doing so, it is possible to conserve energy.
In one form of the invention, as the aforementioned superheated steam generation section combusts and burns the fuel, the combusted gas is mixed with the steam when generating the superheated steam.
With this construction, the fuel is combusted in steam at atmospheric pressure, and by mixing this high-temperature combusted gas with steam, the steam is heated above 100xc2x0 C. to generate superheated steam, so hardly any of the thermal energy of the combusted gas is lost, and can immediately be used for superheating the steam, thus making it possible to efficiently heat the steam to obtain superheated steam.
In another form of the invention, the open steam generation section is located at the bottom of the aforementioned housing container, the superheated steam generation section is located above this steam generation section, and this superheated steam generation section mainly heats the steam through radiation heating to generate superheated steam.
With this construction, steam is generated in an open state inside the housing container, and then this steam is heated as is in an open state inside the container to above 100xc2x0 C. through radiation heating, such as by a heating lamp, thus the thermal energy is used efficiently for superheating, making it possible obtain superheated steam with hardly any heat loss.
In yet another form of the invention, there is a means for forming minute water particles, and the minute water particles that are formed through this means are heated to produce steam, and this steam is then further heated to generate superheated steam.
With this construction, mist made up of minute water particles is formed using an oscillator, such as that is used in a quartz resonator, or a sprayer, and steam is obtained by heating these minute water particles. Moreover, the spherical minute water particles absorb thermal energy, making it possible to efficiently generate steam.